MANYAN METHANOL, AN SAMU A SARARIN SAMANIYA A ƘARSHE

Deuterium shi ne nau’in hydrogen mai nauyi (isotope). A cikin taurarinmu (galaxy) akwai kusan ƙwayoyin deuterium 1.6 a kowane ƙwayoyin hydrogen 100,000. Duk da haka a cikin zukatan gizagizan molecules masu sanyi da cunkoso, inda ake haifar taurari, ƙwayoyin halitta masu ɗauke da deuterium na iya zama ninki-ninki da yawa fiye da abin da wannan rabo ke nunawa. A irin wannan ƙarancin zafi, wasu muhimman halayen sinadarai kaɗan suna ci gaba da tura deuterium cikin ƙwayoyin halitta, kuma tasirin yana ƙaruwa da lokaci. Don haka yawan deuterium da ke cikin ƙwaya na iya nuna lokaci da wurin da aka samar da ita.

Babbar ƙwayar halitta da aka fi samu

Methanol (CH₃OH) ita ce “babbar ƙwayar halitta mai sarƙaƙiya” (complex organic molecule) da aka fi samu — ƙwayoyin halitta masu ɗauke da carbon masu atom shida ko fiye — a yankunan da ake samar da taurari. Galibi ana samar da ita ne a cikin ƙanƙarar da ke lulluɓe ƙurar sararin samaniya a lokacin sanyi kafin tauraro ya kunna, kuma ita ce matakin hawa zuwa ƙwayoyin halitta masu sarƙaƙiya fiye da haka.

Methanol tana da ƙwayoyin hydrogen huɗu: uku a ɓangaren carbon ɗinta, ɗaya a ɓangaren oxygen ɗinta. An riga an gano nau’ikan da ke da ƙwayoyin deuterium ɗaya, biyu ko uku a ɓangaren carbon a sararin samaniya. Nau’in da aka maye gurbin dukka da deuterium (fully deuterated), CD₃OD, inda dukkan huɗun deuterium ne, an ɗan nuna alamunsa ne kawai. Hasashen ɗakin bincike na alamar rediyonsa yana nan tun shekarar 2023.

Layuka goma daga IRAS4A2

A. Belloche, na Cibiyar Max Planck ta Falakin Rediyo (Max Planck Institute for Radio Astronomy) a Bonn, da abokan aikinsa daga Turai, Amurka da Asiya sun yi amfani da COMPASS, wani babban bincike da tarin na’urorin hangen nesa na rediyo na ALMA na matasan taurari goma sha ɗaya masu ƙaramin nauyi da ke da “hot corinos” — yankuna masu ɗumi da matsewa inda ƙwayoyin ƙanƙara ke tururi kuma su yi haske a tsawon igiyoyin rediyo. Sun mai da hankali kan IRAS4A2, ɗaya daga cikin tauraron biyu a cikin gajimaren NGC 1333, mai nisan parsec 290. A nan ne kuma aka fara gano ammonia da aka maye gurbin dukka da deuterium a kewayen wani matashin tauraro.

Ta hanyar duba mitocin sama daga gigahertz 279 zuwa 312, tawagar ta yi samfurin hasken methanol da dukkan nau’ikanta a zafin kusan kelvin 200. Kowane nau’in methanol da ke da sanannen alamar rediyo ya bayyana. Daga cikinsu: CD₃OD, da layuka goma da aka gano a fili. Wannan shi ne ganowa na farko mai ƙarfi na methanol da aka maye gurbin dukka da deuterium a sararin samaniya — kuma, marubutan sun lura, gano farko na kowace ƙwayar halitta mai ɗauke da ƙwayoyin deuterium huɗu a sararin tsakanin taurari. Yana kai kusan kashi 4 cikin 10,000 na methanol da ke can.

Methanol da ke ɓoyewa

Wani abin mamaki ya zo tare da shi. Idan aka kwatanta da nau’ikanta da ba safai ake samu ba na carbon-13 da oxygen-18, methanol na yau da kullum ya yi kamar ya yi ƙaranci ƙwarai — kusan sau 7 zuwa 11 ƙasa da yadda ya kamata — alhali nau’ikan da ba safai ake samu ba sun yi daidai da juna yadda ya dace. Marubutan sun kammala cewa mai yiwuwa an rage ƙiyasin yawan methanol na yau da kullum, watakila saboda haskensa yana fitowa ne daga dunƙule-dunƙule maimakon gajimare mai santsi. Don haka sun yi amfani da nau’ikan da ba safai ake samu ba a matsayin madadin don lissafa rabon deuterium.

Deuterium yana taruwa fiye da kwatsam

Da a ce deuterium yana maye gurbin hydrogen ne kawai ba da tsari ba da wata tabbatacciyar yiwuwa, kowane nau’i zai nuna rabon deuterium da hydrogen iri ɗaya. Maimakon haka, rabon da aka ƙiyasta yana hawa tare da yawan ƙwayoyin deuterium: kusan kashi 1% ga nau’ikan da ke da deuterium ɗaya, kashi 9 zuwa 23% ga masu deuterium biyu da uku, kuma kusan kashi 41% idan aka kwatanta CD₃OD da CH₃OD. Tsarin a IRAS4A2 kusan iri ɗaya ne da na wani matashin tauraro, BHR71-IRS1, kuma yana kama da na sauran taurarin da ke tasowa (protostars) masu ƙaramin nauyi.

Samfura sun kasa kai wa ga ɓangaren mai nauyi

Tawagar ta kwatanta waɗannan rabo da samfuran sinadarai guda biyar da aka wallafa kan yadda methanol da nau’ikanta masu deuterium ke haɓaka. Dukkansu sun rage ƙiyasin nau’ikan da ke da deuterium da yawa, yawanci da ninki goma zuwa ninki ɗari — kuma, ga CD₃OD a cikin samfuri ɗaya, da kusan ninki dubu ɗari (orders of magnitude biyar). Hukuncin marubutan: akwai wani muhimmin sinadari da ke haɓaka methanol mai deuterium da yawa da ya ɓace daga samfuran yanzu.

Ganowar ta kuma yi hasashe. Sauran nau’ikan biyu, CH₂DOD da CHD₂OD, ya kamata a sauƙaƙe gano su a IRAS4A2 da zarar masana nazarin bakan haske (spectroscopists) a ɗakin bincike suka samar da alamominsu na rediyo. Duba da kyau da ƙuduri mafi girma (angular resolution) zai iya bayyana ko methanol ɗin da gaske yana cikin dunƙule-dunƙule.